Mirror box and electronic still camera

ABSTRACT

A mirror box includes a mirror that is selectively set to one of a reflecting position, which is on an optical path between a photographing lens and an imaging device so that incident light passing through the photographing lens is reflected to a view-finder, and a retracted position, which is out of the optical path so that said incident light is led to the imaging device. A filter is selectively set to one of a non-functioning position, which is close to the mirror, when the mirror is set to the reflecting position, and a functioning position, which is on the optical path so that a predetermined light component contained in the incident light is blocked, when the mirror is set to the retracted position. The filter comprises an optical low-pass filter, and the mirror comprises a half-mirror which is integrally provided on an incident surface of the optical low-pass filter.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional application of pending U.S.patent application Ser. No. 09/984,728, filed on Oct. 31, 2004, whichclaims priority based upon Japanese Application No. 2000-361761, filedDec. 15, 2000, the contents of which are expressly incorporated byreference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mirror box, which is mounted in anelectronic still camera, to lead light entering through a photographinglens selectively to a view-finder or an imaging device such as a CCD.

2. Description of the Related Art

Conventionally, there is known an electronic still camera which is asingle-lens reflex type. The single-lens reflex camera is provided witha quick return mirror, which is set on an optical path between thephotographing lens and the imaging device, to lead the incident lightfrom the photographing lens the view-finder. Conversely, in aphotographing operation, the quick return mirror is retracted from theoptical path, so that a subject image is formed on the imaging device.

In an electronic still camera which utilizes a CCD as the imagingdevice, an optical low-pass filter removing a high-frequency componentis fixed between the photographing lens and the CCD, so as to preventthe generation of moiré fringes. Moiré fringes occur when the incidentlight has a high-frequency component, so that the image quality islowered. similarly, an infrared cut filter may be provided forpreventing the deterioration of exact color reproduction, which occursbecause of infrared light.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a mirror boxwhich is mounted in a single-lens reflex type electronic still camera,and which compactly houses a quick return mirror and an optical low-passfilter.

According to the present invention, there is provided a mirror boxcomprising a mirror that is selectively set to one of a reflectingposition and a retracted position, and a filter that is selectively setto one of a non-functioning position and a functioning position.

The reflecting position is on an optical path between a photographinglens and an imaging device so that incident light passing through thephotographing lens is reflected to a view-finder. The retracted positionis out of the optical path so that the incident light is led to theimaging device. The non-functioning position is close to the mirror,when the mirror is set to the reflecting position. The functioningposition is on the optical path so that a predetermined light componentcontained in the incident light is blocked, when the mirror is set tothe retracted position.

The predetermined light component may contain a high-frequencycomponent, and may contain an infrared wave length component.

The filter may comprise an optical low-pass filter, and the mirror maycomprise a quick return mirror which is separately provided from theoptical low-pass filter.

The mirror box may further comprise a drive mechanism that drives themirror and the filter in association with each other. Preferably, thedrive mechanism comprises a motor, a first gear, a first arm, a secondgear, and a second arm. The first gear rotates in association with themotor, and has a first cam groove. The first arm has a first camfollower engaged with the first cam groove. The first cam follower ismoved along the first cam groove so that the mirror is moved between thereflecting position and the retracted position. The second gear rotatesin association with the motor, and has a second cam groove. The secondarm has a second cam follower engaged with the second cam groove. Thesecond cam follower is moved along the second cam groove so that thefilter is moved between the non-functioning position and the functioningposition.

The reflecting position may be inclined by substantially 45 degrees tothe optical axis of the photographing lens, the retracted position issubstantially parallel to the optical axis, the non-functioning positionis behind the mirror and is parallel to the mirror when the mirror isset to the reflecting position, and the functioning position isperpendicular to the optical axis.

The filter may comprise an optical low-pass filter, and the mirror maycomprise a half-mirror which is integrally provided on an incidentsurface of the optical low-pass filter.

Further, according to the present invention, there is provided anelectronic still camera comprising a view-finder through which a subjectimage obtained by a photographing lens can be observed, a half mirrorthat is integrally provided with an optical low-pass filter, and aview-finder shutter.

The half mirror is integrally provided with an optical low-pass filter.The half mirror is provided between the photographing lens and animaging device. The half mirror is moved between a first position, atwhich incident light passing through the photographing lens is reflectedto the view-finder, and a second position, at which a predeterminedlight component contained in the incident light is blocked, to lead theincident light to the imaging device. The view-finder shutter isprovided between the view-finder and the half mirror. The view-findershutter blocks light when the half mirror is set to the second position.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and advantages of the present invention will be betterunderstood from the following description, with reference to theaccompanying drawings in which:

FIG. 1 is a sectional view of an electronic still camera to which afirst embodiment is applied, and which is in a subject observing state;

FIG. 2 is a sectional view of the electronic still camera which is setin a photographing operation;

FIG. 3 is a view showing a drive mechanism when a subject image isobserved;

FIG. 4 is a view showing the drive mechanism when a photographingoperation is performed;

FIG. 5 is a flowchart of an operation of the electronic still camera ina photographing operation;

FIG. 6 is a sectional view of an electronic still camera to which asecond embodiment is applied; and

FIG. 7 is a flowchart of an operation of the electronic still camera ina photographing operation, to which the second embodiment is applied.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described below with reference to anembodiment shown in the drawings.

FIG. 1 shows an electronic still camera to which a first embodiment isapplied, and which is set in a subject observing state.

A shutter button 11 is provided on an upper surface of a camera body 10of the electronic still camera. A lens barrel 20, in which aphotographing lens group 21 is housed, is detachably connected to afront surface of the camera body 10. Incident light passing through thephotographing lens group 21 is subjected to a light amount adjustment byan aperture (not shown), and enters the camera body 10.

A CCD 50, which is an imaging device, is mounted in the camera body 10,and a mirror box 30 is disposed on an optical path between the CCD 50and the photographing lens group 21. The mirror box 30 is provided forleading the incident light to the CCD 50 or a view-finder 40 disposedabove the mirror box 30, in which a quick return mirror 31 and anoptical low-pass filter 32 are housed in order, when viewed from thephotographing lens group 21.

The quick return mirror 31 is a plane mirror, and is set to a reflectingposition, which is on the optical path and inclined by substantially 45degrees to the optical axis of the photographing lens group 21. Thequick return mirror 31 at the reflecting position totally reflects theincident light, passing through the photographing lens group 21 and afirst opening 34K formed between the lens barrel 20 and the mirror box30, to the view-finder 40. The reflected incident light passes through asecond opening 34F and is led to a focusing glass 33, so that a subjectimage is formed on the focusing glass 33. The subject image can beobserved through a pentagonal prism 41 and an eyepiece 42.

The optical low-pass filter 32 is a flat plate slightly smaller than thequick return mirror 31. The optical low-pass filter 32 is a crystalliquid plate filtering a high-frequency component, and is made of aquarts plate, for example. In the embodiment, an infrared filterblocking an infrared light component is adhered on the optical low-passfilter 32. Therefore, a high-frequency component and an infrared lightcomponent contained in light entering the optical low-pass filter 32 areremoved, and are led to the CCD 50. When the quick return mirror 31 isset to the reflecting position, the optical low-pass filter 32 is set toa non-functioning position, which is close to the quick return mirror31. The non-functioning position is behind the quick return mirror 31,and is parallel to the quick return mirror 31. In this state, theincident light is totally reflected by the quick return mirror 31, andthus, is not led to the optical low-pass filter 32 nor the CCD 50.

A shutter 51 provided between the mirror box 30 and the CCD 50. Theshutter 51 has a shutter curtain 51A composed of some plates, and ashutter curtain housing unit 51B in which the shutter curtain 51A ishoused. When a subject image is observed, the shutter curtain 51A ispositioned to cut the optical path to block the light to the CCD 50.

FIG. 2 shows the electronic still camera is set in a photographingoperation.

In the photographing operation, the shutter button 11 is depressed, sothat the quick return mirror 31 is moved from the reflecting positionshown in FIG. 1 to a retracted position, which is out of the opticalpath, and in which the quick return mirror 31 is parallel to a focusingglass 33 to retract from the optical path. Thus, the quick return mirror31 closes the second opening 34F, so that the incident light cannotenter the view-finder 40. Accordingly, the subject image cannot beobserved through the eyepiece 42, and thus a blackout state occurs inthe view-finder 40. Further, at this time, light entering the eyepiece42 is blocked by the quick return mirror 31, and cannot be received bythe CCD 50 through the second opening 34F.

On the other hand, the optical low-pass filter 32 is moved from thenon-functioning position shown in FIG. 1 to a functioning position, inwhich the optical low-pass filter 32 is perpendicular to the opticalaxis of the photographing lens group 21. In this movement, the opticallow-pass filter 32 does not contact the quick return mirror 31 which isset to the retracted position. The incident light enters the opticallow-pass filter 32 set to the functioning position, so that ahigh-frequency component and an infrared wave length component areremoved from the incident light, and thus the incident light is led tothe CCD 50 through a third opening 34C formed in the mirror box 30.

Thus, the optical low-pass filter 32 is moved to the functioningposition only in the photographing operation, and is set to thenon-functioning position when the subject image is observed. Due tothis, the quick return mirror 31 and the optical low-pass filter 32 canbe provided close to each other. Namely, in comparison with a case inwhich the optical low-pass filter 32 is always fixed in a specificposition and is parallel to the CCD 50, the quick return mirror 31 andthe optical low-pass filter 32 can be housed in a narrow space.

In the shutter 51, the shutter curtain 51A is housed in the shuttercurtain housing unit 51B, so that the CCD 50 is exposed for apredetermined time of period. Thus, the incident light from which ahigh-frequency component is removed is led to the CCD 50 to sense asubject image.

FIG. 3 shows a drive mechanism which drives the quick return mirror 31and the optical low-pass filter 32 when the subject image is observed.

An upper end portion 31A of the quick return mirror 31 is rotatablyconnected to a mirror support shaft 61, which is integrally provided inthe mirror box 30. The quick return mirror 31 is rotated between thereflecting position and the retracted position about the mirror supportshaft 61. A mirror urging spring 63 is wound around the mirror supportshaft 61. One end portion 63A of the mirror urging spring 63 is engagedwith a first spring fixation member 67 provided in the mirror box 30,and the other end portion 63B is engaged with a mirror projection 64provided in the quick return mirror 31. The mirror urging spring 63urges the mirror projection 64 in a direction in which the end portions63A and 63B are separated from each other, i.e., in which the mirrorprojection 64 parts from the first spring fixation member 67. Due tothis, the quick return mirror 31 is urged in the clockwise direction inthe drawing. On the other hand, a lower end portion 31B of the quickreturn mirror 31 is engaged with a mirror stopper 62 provided at aposition under the mirror support shaft 61. Due to this, the quickreturn mirror 31 is fixed at the reflecting position, so that theincident light is totally reflected to the view-finder 40 as shown by achain double-dashed line in the drawing.

A motor (not shown) for rotating the quick return mirror 31 is mountedin the mirror box 30. A dive gear 80 is fixed on an output shaft of themotor. The drive gear 80 is meshed with a first gear 66, so that thefirst gear 66 is rotated by the motor.

A first cam groove 68 is formed on a side surface of the first gear 66.The first cam groove 68 has an arc portion 68A and two straight portions68B and 68C. The straight portions 68B and 68C are connected to eachother at end portions thereof, and the other end portions of thestraight portions 68B and 68C are connected by the arc portion 68A. Thebreadth of the first cam groove 68 is constant over the whole periphery.The arc portion 68A is formed along the outer periphery of the firstgear 66, and is extended to cover a range of approximately 160 degreesfrom the central angle. A connecting portion 68D formed between thestraight portions 68B and 68C is positioned opposite to the arc portion68A with respect to the rotation center 66M of the first gear 66. Thedistance from the rotation center 66M to each of the straight portions68B and 68C is essentially shorter than that from the rotation center66M to the arc portion 68A.

A first arm 65 is provided beside the first gear 66, and extendedbetween the first cam groove 68 and the mirror projection 64. A pin 65Mfixed on a center portion of the first arm 65 is rotatably supported bythe mirror box 30, so that the first arm 65 can be rotated about the pin65M. A first cam follower 69 fixed to an end portion of the first arm 65is engaged with the first cam groove 68, so that the first arm 65 isrotated about the pin 65M due to the change of the position of the firstcam follower 69 when the first gear 66 is rotated.

In FIG. 3, the first cam follower 69 is engaged with the connectingportion 68D, and a lower end portion 65A of the first arm 65 ispositioned close to the rotation center 66M of the first gear 66, sothat the first arm 65 is inclined relative to the optical axis byapproximately 30 degrees. At this time, the other end portion 65B of thefirst arm 65 is kept to abut against the mirror projection 64.

On the other hand, the optical low-pass filter 32 has a similarstructure to the quick return mirror 31. Namely, a lower end portion 32Aof the optical low-pass filter 32 is rotatably connected to a filtersupport shaft 71. Thus, the optical low-pass filter 32 is rotatedbetween the non-functioning position and the functioning position aboutthe filter support shaft 71. A filter urging spring 76 is wound aroundthe filter support shaft 71. One end portion 76A of the filter urgingspring 76 is engaged with a second spring fixation member 77 provided tothe mirror box 30, and the other end portion 76B is engaged with afilter projection 73 provided to the optical low-pass filter 32. Thefilter urging spring 76 urges the filter projection 73 in a direction inwhich the end portions 76A and 76B are separated from each other, sothat the optical low-pass filter 32 is urged in the clockwise directionin the drawing.

A second gear 75 is meshed with an opposite portion of the drive gear 80relative to the first gear 66. A second cam groove 78 is formed on aside surface of the second gear 75. A second arm 74 is provided besidethe second gear 75, and is rotatable about a pin 74M fixed on a centerportion thereof. A second cam follower 79 fixed to an end portion of thesecond arm 74 is engaged with the second cam groove 78, so that thesecond arm 74 is rotated about the pin 74M when the second gear 75 isrotated.

In FIG. 3, the second cam follower 79 is engaged with an arc portion 78Aof the second cam groove 78, so that an upper end portion of the secondarm 74 is positioned close to the drive gear 80. In this state, a lowerend portion 74B of the second arm 74 presses the filter projection 73against the spring force of the filter urging spring 76, so that arotation of the optical low-pass filter 32 in the clockwise direction isprevented.

FIG. 4 shows the drive mechanism when a photographing operation isperformed.

When the release button 11 is depressed, the motor is actuated, so thatthe drive gear 80 is rotated in the counter clockwise direction as shownby an arrow X. Due to this, the first gear 66 is rotated in theclockwise direction shown by an arrow Y, and the second gear 75 issimultaneously rotated in the clockwise direction shown by an arrow Z.

By the clockwise rotation of the first gear 66, the first cam follower69 is moved from the connecting portion 68D to the arc portion 68Athrough the straight portion 68B. When the first cam follower 69 isengaged with the straight portion 68B, the lower end portion 65A of thefirst arm 65 is positioned close to the rotation center 66M, similarlyto the case shown in FIG. 3. Then, when the first cam follower 69approaches a connecting portion 68E at which the straight portion 68Band the arc portion 68A are connected to each other, the lower endportion 65A of the first arm 65 is positioned further from the rotationcenter 66M of the first gear 66, so that the lower end portion 65A ispressed downward. Therefore, the first arm 65 is rotated in theclockwise direction about the pin 65M to rise relative to the opticalaxis. Thus, the other end portion 65B of the first arm 65 presses themirror projection 64 against the spring force of the mirror urgingspring 63, so that the quick return mirror 31 is rotated in the counterclockwise direction about the mirror support shaft 61.

On the other hand, by the rotation of the second gear 75 in the Zdirection, the second cam follower 79 is moved from the arc portion 78Aof the second cam groove 78 to a straight portion 78C. When the secondcam follower 79 is engaged with the straight portion 78C, the second camfollower 79 is pulled toward a rotation center 75M of the second gear 75while the second gear 75 is rotated, so that an upper end portion 74A ofthe second arm 74 is urged downward. Therefore, the second arm 74 isrotated about the pin 74M in the counter clockwise direction. Due tothis, the filter projection 73 is urged by the filter urging spring 76,so that the optical low-pass filter 32 is rotated in the clockwisedirection

When the first cam follower 69 reaches the arc portion 68A, and thesecond cam follower 79 reaches a connecting portion 78D at which thestraight portions 78B and 78C are connected, the first arm 65 and thesecond arm 74 are stopped at positions shown in FIG. 4. Namely, thequick return mirror 31 is set to the retracted position, and the opticallow-pass filter 32 is set to the functioning position, where the opticallow-pass filter 32 is supported by a stopper not shown to keep thefunctioning position.

After the photographing operation is completed, the drive gear 80 isrotated in the counter clockwise direction by the motor, so that thefirst and second gears 66 and 75 are rotated in the clockwise direction.As a result, the first cam follower 69 is moved from the arc portion 68Ato the straight portion 68C, and the second cam follower 79 is movedfrom the connecting portion 78D to the arc portion 78A through thestraight portion 78B, so that the drive mechanism returns to the initialstate shown in FIG. 3.

Thus, in the photographing operation, the quick return mirror 31 ischanged from the reflecting position to the retracted position, and atthe same time, the optical low-pass filter 32 is set to the functioningposition. The condition of the photographing operation, shown in FIG. 4,is maintained from a time when the release button 11 is depressed to atime when a predetermined exposure period of the CCD 50 has elapsed.When the photographing operation is completed, the quick return mirror31 is changed from the retracted position to the reflecting position,and the optical low-pass filter 32 is changed from the functioningposition to the non-functioning position. Thus, the drive mechanismdrives the quick return mirror 31 and the optical low-pass filter 32 inassociation with each other.

FIG. 5 is a flowchart of an operation of the electronic still camera ina photographing operation.

By turning ON an electric power switch (not shown) provided to thecamera body 10, it is determined in Step 101 whether the release button11 has been depressed or not. When it is determined that the releasebutton 11 has been depressed, Step 102 is executed, in which the quickreturn mirror 31 is moved up from the optical path to the retractedposition. In Step 103, then, the optical low-pass filter 32 is raisedand set to the functioning position, so that the incident light is ledto the optical low-pass filter 32.

In Step 104, the shutter curtain 51A is housed in the shutter curtainhousing unit 51B, so that the shutter 51 is open. Therefore, in Step105, the CCD 50 is exposed so that incident light from which ahigh-frequency component and an infrared light component are removed isled to the CCD 50. Thus, a sensing operation of a subject image iscompleted, and thus, the process goes to Step 106, so that the conditionreturns to the subject observing condition.

In Step 106, the shutter curtain 51A is moved to the optical path, sothat the shutter 51 closes the optical path. In Step 107, the opticallow-pass filter 32 is set to the non-functioning position. In Step 108,the quick return mirror 31 is set to the reflecting position, to returnto the subject observing condition.

It is determined in Step 109 whether the photographing operation is tobe completed, i.e., whether the electric power switch is turned OFF.When it is determined that the completion of the photographing operationhas been selected, a photographing operation completion process iscarried out, so that the photographing operation ends. Conversely, whenit is determined that the completion of the photographing operation hasnot been selected, the process goes back to Step 101, and the processwaits until the release button 11 is depressed.

As described above, according to the first embodiment, the quick returnmirror 31 and the optical low-pass filter 32 can be disposed close toeach other, and thus, the length of the mirror box 30 in the opticalaxial direction can be reduced.

A second embodiment will be described below with reference to FIGS. 6and 7. Although the quick return mirror 31 is separately provided fromthe optical low-pass filter in the first embodiment a half-mirrorintegrated filter 91, in which an optical low-pass filter 91A and ahalf-mirror 91B are integrally provided, is mounted in a mirror box 90in the second embodiment. FIG. 6 is a sectional view of an electronicstill camera of the second embodiment. Note that the corresponding partsto the first embodiment are indicated by the same reference numerals asthose of the first embodiment.

In the mirror box 90, the half-mirror integrated filter 91 is located onthe optical path between the photographing lens group 21 and the CCD 50.In the half-mirror integrated filter 91, the half-mirror 91B isintegrally provided on an incident surface of the optical low-passfilter 91A.

The optical low-pass filter 91A is a crystal plate filtering ahigh-frequency component, similarly to the first embodiment, and aninfrared cut filter for filtering an infrared component is adhered onthe optical low-pass filter. The half-mirror 91B is a plane mirror,which reflects approximately a half of the incident light and passes theremaining half. Namely, in the incident light entering the half-mirrorintegrated filter 91, approximately a half of the light is reflected bythe half-mirror 91B and the remaining half passes through thehalf-mirror 91B. The incident light passing through the half-mirror 91Bhas a high-frequency component and an infrared component removed, and isled to the CCD 50.

When observing a subject image, the half-mirror integrated filter 91 isset to a first position, which is inclined relative to the optical axisof the photographing lens group 21 by approximately 45 degrees. Due tothis, approximately a half of the light reflected by the half-mirror 91Bis led to the view-finder 40, so that a subject image is formed on thefocusing glass 33. Conversely, although the incident light from which ahigh-frequency component and an infrared component are removed by theoptical low-pass filter 91A is led to the CCD 50, since the shutter 51is closed, the incident light is blocked by the shutter curtain 51A, anddoes not enter the CCD 50.

When carrying out a photographing operation, the half-mirror integratedfilter 91 is rotated and rises in a direction shown by an arrow S (i.e ,the clockwise direction in FIG. 6) about a lower end portion 91C, and isset to a second position which is perpendicular to the optical axis. Inassociation with this rotation of the filter 91, the shutter 51 is fullyopen. Due to this, the incident light enters the half-mirror integratedfilter 91 in a vertical direction. Namely, the incident light passesthrough the half-mirror integrated filter 91, so that a subject image isformed on the CCD 50. The incident light is not led to the focusingglass 33, since the half-mirror integrated filter 91 is upright.

In the view-finder 40, a view-finder shutter 92 is mounted between thepentagonal prism 41 and the eyepiece 42. The view-finder shutter 92 hasa view-finder shutter curtain 92A and a view-finder shutter curtainhousing unit 92B. The view-finder shutter curtain 92A is composed ofsome plates. When observing a subject image, the view-finder shuttercurtain 92A is housed in the view-finder shutter curtain housing unit92B, so that the subject image can be observed through the eyepiece 42.When the release button 11 is depressed, the view-finder shutter curtain92A is set between the eyepiece 42 and the pentagonal prism 41 to blocklight entering through the eyepiece 42. Thus, light entering theeyepiece 42 is prevented from reaching the CCD 50.

FIG. 7 is a flowchart of an operation of the electronic still camera ina photographing operation of the second embodiment.

By turning ON an electric power switch (not shown) provided on thecamera body 10, it is determined in Step 201 whether the release button11 has been depressed or not. When it is determined that the releasebutton 11 has been depressed, Step 202 is executed in which theview-finder shutter curtain 92A is moved to a position to block lightentering the eyepiece 42, and closes the view-finder shutter 92. In Step203, the half-mirror integrated filter 91 is raised to the secondposition. In Step 204, the shutter curtain 51A is housed in the shuttercurtain housing unit 513. Therefore, in Step 205, the CCD 50 is exposedso that a subject image is sensed. Thus, a sensing operation of asubject image is completed, and the process goes to Step 206, so thatthe condition returns to the subject observing condition.

In Step 206, the shutter curtain 51A is moved to the optical path, sothat the shutter 51 closes the optical path. In Step 207, thehalf-mirror integrated filter 91 is moved from the second position tothe first position. In Step 208, the view-finder shutter curtain 92A ishoused in the view-finder shutter curtain housing unit 92B, so that theview-finder shutter 92 is open, to return to the subject observingcondition.

It is determined in Step 209 if the photographing operation is to becompleted. When it is determined that the completion of thephotographing operation has been selected, a photographing operationcompletion process is carried out. Conversely, when it is determinedthat the completion of the photographing operation has not beenselected, the process goes back to Step 201, and the process waits untilthe release button 11 is depressed.

According to the second embodiment, the half-mirror 91B integrated withthe optical low-pass filter 91A is utilized instead of the quick returnmirror, and the quick return mirror does not have to be provided.Accordingly, the mirror box 90 is miniaturized, and further thestructure of the drive mechanism becomes simple, in comparison with thefirst embodiment.

Note that, in the second embodiment, the view-finder shutter 92 has tobe provided at a position so that light entering the eyepiece 42 doesnot reach the CCD 50. Further, the half-mirror integrated filter 91 maybe fixed at the first position (not moved to the second position), ifthe half-mirror integrated filter 91 leads the incident light to both ofthe view-finder 40 and the CCD 50 in a state in which the half-mirrorintegrated filter 91 is positioned at the first position.

Although the embodiments of the present invention have been describedherein with reference to the accompanying drawings, obviously manymodifications and changes may be made by those skilled in this artwithout departing from the scope of the invention.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2000-381761 (filed on Dec. 15, 2000) which isexpressly incorporated herein, by reference, in its entirety.

1. A mirror box comprising: a mirror that is selectively set to one of areflecting position, which is on an optical path between a photographinglens and an imaging device so that incident light passing through saidphotographing lens is reflected to a view-finder, and a retractedposition, which is out of said optical path so that said incident lightis led to said imaging device; and a filter that is selectively set toone of a non-functioning position, which is close to said mirror, whensaid mirror is set to said reflecting position, and a functioningposition, which is on said optical path so that a predetermined lightcomponent contained in said incident light is blocked, when said mirroris set to said retracted position, said filter comprising an opticallow-pass filter, and said mirror comprising a half-mirror which isintegrally provided on an incident surface of said optical low-passfilter.
 2. A mirror box according to claim 1, wherein said predeterminedlight component contains a high-frequency component.
 3. A mirror boxaccording to claim 1, wherein said predetermined light componentcontains an infrared wavelength component.
 4. A mirror box according toclaim 1, further comprising a drive mechanism that drives said mirrorand said filter between their respective positions.
 5. A mirror boxaccording to claim 1, wherein said reflecting position is inclined bysubstantially 45 degrees with respect to the optical axis of saidphotographing lens, said retracted position is substantially parallel tothe optical axis, said non-functioning position is behind said mirrorand is parallel to said mirror when said mirror is set to saidreflecting position, and said functioning position is perpendicular tothe optical axis.
 6. The mirror box according to claim 1, the opticallow-pass filter comprising a crystal plate that filters a high frequencycomponent and an infrared cut filter that filters an infrared component.7. An electronic still camera comprising: a view-finder through which asubject image obtained by a photographing lens can be observed; a halfmirror that is integrally provided with an optical low-pass filter, saidhalf mirror being provided between said photographing lens and animaging device, and movable between a first position, at which incidentlight passing through said photographing lens is reflected to saidview-finder, and a second position, at which a predetermined lightcomponent contained in said incident light is blocked to lead saidincident light, without the predetermined light component, to saidimaging device; and a view-finder shutter that is provided between saidview-finder and said half mirror, said view-finder shutter blockinglight when said half mirror is set to said second position.
 8. A mirrorbox according to claim 7, wherein said predetermined light componentcontains a high-frequency component.
 9. A mirror box according to claim7, wherein said predetermined light component contains an infraredwavelength component.
 10. A mirror box according to claim 7, the opticallow-pass filter comprising a crystal plate that filters a high frequencycomponent and an infrared cut filter that filters an infrared component11. A mirror box according to claim 7, further comprising a drivemechanism that drives said half-mirror and said optical low-pass filterbetween the first and second positions.
 12. A mirror box according toclaim 7, wherein said first position is inclined by substantially 45degrees to the optical axis of said photographing lens and said secondposition is substantially perpendicular to the optical axis.